The invention relates generally to an earth moving device in the form of a tractor-drawn scraper into which soil is propelled by an elevator and which has improved means for dumping the soil when the scraper bowl is filled.
When operating under wet conditions, or in clayey soils, the soil which is collected in the scraper bowl is not easily dislodged. It has been the practice in the past to employ a floor having a fixed rear section and a rearwardly sliding front section to uncover a front discharge opening. The back wall of the bowl is commonly in the form of an ejector plate which is thrust forwardly by actuators to push the soil into a position over the front opening. The effect of the ejector plate is often to compact the soil into a tight mass which becomes firmly stuck to the side sheets of the bowl and tightly jammed into the flights of the elevator, both effects, combined with the relatively small area of the opening, tending to cause the soil to become "hung-up" in the bowl. Moreover, it is found that when using bowls having a length which is greater than the width dimension, the tendency of the mass of soil to expand outwardly toward the side walls, in the case of clayey soils, produces a bracing reaction which may be sufficiently strong as to block the ejector plate completely against further forward movement. Thus while conventional elevator-type scrapers work very well in soils which are relatively dry and friable, it is sometimes necessary, in the case of wet clayey soils, to suspend operations temporarily until the soil loses some of its moisture. Such lost time is costly to the contractor.
It is, moreover, a common expedient in devices of this type to mount the scraper blade at the front edge of the rearwardly slidable floor section so that it, upon retraction, may also serve as a spreader or strike-off device. However, the modern tendency to use relatively narrow scraper blades with projecting ripper teeth to engage the subsoil precludes smooth full-width strike-off or leveling. Also, when the scraper blade is mounted on the forward edge of a rearwardly slidable floor section, the floor section and its mounting must be made quite massive in order to absorb reaction forces, without any benefit to the bowl structure. Then too, where an ejector plate is used in lieu of a back wall, the side sheets cannot rely upon the back wall for lateral bracing so that the bowl tends to be weakened at the back as well as the front. To this must be added the fact that, where an ejector plate is used, provision must be made behind the plate, and between the rear wheels, for relatively massive actuators and actuator mounting elements which, in the case of a scraper having a rear engine, results in serious space and design complications.